TranS1 Surges in Public Debut

Editor's Note: In this feature from Stockpickr, we highlight lists of stocks that have been upgraded or downgraded by analysts or are experiencing activist-investor situations or some other market-moving events.

Rumors of the Day: Reinvigorated buyout rumors moved Marriott ( MAR). Recent consolidation in the hotel industry has prompted speculation that Marriott could be the next target of a private equity bid. Shares of Marriott were trading down 2.1% at $41.25 Wednesday after climbing Tuesday.

TranS1 ( TSON) debuted with a flourish on the Nasdaq Wednesday. Shares of the medical device company -- which priced 5.5 million shares at $15, above the expected $12 to $14 range -- are now trading more than 60% higher at $24.40.

Analyst Downgrades: Cowen downgraded Level 3 ( LVLT) from outperform to neutral and also cut its estimates, as acquisitions are taking longer than expected to integrate. Shares of the communication services company recently fell 2.1% to $4.17.

Analyst Upgrades: Deutsche Bank upgraded US Steel ( X) with a buy rating and raised its price target to $130. The bank also raised its 2008 earnings estimate to $13 a share to reflect rising steel prices. Shares of the steelmaker were climbing 2.1% to $106.58 in recent trading.

Latest Activist Situations: The Children's Investment Master Fund, a 4.1% shareholder in CSX Corp. ( CSX), is pressuring the railroad's board of directors to improve the company's business performance. The activist fund is requesting that the chairman and CEO roles be separated and the board "refreshed" with new independent directors. Shares of CSX shot up 6% to $45.40.